Grounding Connection For Outlet Box

Abstract

A spring metal clip mounted to connect the metal frame portion and ground terminal of an electrical receptacle unit to make spring contact with the box or may be connected to the box to make spring contact with a metal frame portion of the unit.

Description

This invention relates to electrical connection devices, and more particularly to connectors for establishing electrical connections between the ground terminals of electrical receptacle units or switch units with their associated metal housings.

A main object of the invention is to provide a novel and improved connection means for providing a reliable ground connection between an electrical unit, such as a receptacle or switch, and its associated metal housing box, the connection means being simple in construction, being easy to install, and occupying very little space in the associated metal outlet or receptacle box.

A further object of the invention is to provide an improved ground connector for establishing a ground connection between the metal frame portion or ground terminal of an electrical receptacle unit or switch unit and its associated metal housing, the device being inexpensive to fabricate, being durable in construction, being capable of being installed with minimum effort and in a very short period of time, and providing a safe and reliable ground connection which conforms with present code requirements.

A still further object of the invention is to provide an improved connection device for establishing a reliable ground connection between a receptacle or switch unit and its associated outlet box, the ground connection device providing a conductive connection between the associated electrical unit and its box so as to provide safe operation of electrical equipment energized from the receptacle unit or controlled therefrom, and so as to provide reliable grounding of exposed metal parts, whereby to reduce fire and shock hazards and to provide grounding of the frame portions of equipment associated with the electrical units, such as power tools, office equipment, fans, air conditioners, heaters, and the like, which may be energized from or controlled by the electrical unit.

Further objects and advantages of the invention will become apparent from the following description and claims, and the accompanying drawings, wherein:

FIG. 1 illustrates a typical electrical receptacle unit and its associated metal housing box, with the inclusion of an improved grounding device attached to the receptacle unit and being adapted to engage the interior of its grounding box when the unit is installed in the box.

FIG. 2 is a longitudinal vertical cross-sectional view taken through the electrical receptacle unit and its associated housing box with the unit installed in operating position in the box.

FIG. 3 is a perspective view of the metal grounding clip employed in FIGS. 1 and 2.

FIG. 4 is a longitudinal cross-sectional view, similar to FIG. 2, but showing the use of a modified form of metal grounding clip.

FIG. 5 is a vertical cross-sectional view taken substantially on the line 5--5 of FIG. 4.

FIG. 6 is a fragmentary plan view taken substantially on the line 6--6 of FIG. 4.

FIG. 7 is a somewhat enlarged perspective view of the spring grounding clip employed in FIGS. 4, 5 and 6.

FIG. 8 is a fragmentary vertical cross-sectional view showing another form of spring grounding clip employed to connect an electrical receptacle unit to its associated metal housing box, in accordance with the present invention.

FIG. 9 is a vertical cross-sectional view taken substantially on line 9--9 of FIG. 8.

FIG. 10 is an enlarged perspective view of the spring grounding clip employed in FIGS. 8 and 9.

Referring to the drawings, and more particularly to FIGS. 1, 2, and 3, 11 designates the conventional electrical receptacle unit of the type provided with ground apertures 12 to receive the ground prongs of conventional plugs associated with electrical appliances, the purpose of the ground prongs being to connect the exposed metal portions of the appliances to a suitable ground connection. Thus, receptacle 11 is internally provided with a contact sleeve to receive the ground prong of such a plug. The ground terminals of the receptacle 11 are connected to a conductor 13 which is provided with a terminal screw 14 to enable the receptacle ground terminals to be connected to a suitable ground connection, for example, to the associated grounded metal outlet box 15 in which receptacle 11 is to be installed.

In accordance with the present invention, a spring metal clip 16 is attached to the conductor 13 by means of the terminal screw 14, the clip 16 being arranged to make conductive contact with a wall 17 of the associated outlet box 15.

As shown in FIG. 3, the spring clip 16 comprises a length of suitable spring rod material, such as resilient metal wire formed at its top end with a circular loop or eye 18 and having a depending bottom loop in hook form, shown at 19, connected to the top loop 18 by an offset portion 20. As shown in FIG. 2, when the loop 18 is connected to the conductor 13 by the terminal screw 14 and the screw 14 is tightened, the bottom loop 19, which is located in a plane transverse to the plane of the top loop 18, extends forwardly from the adjacent end of the receptacle unit 11 and is in a position to resiliently engage the adjacent end wall 17 of the associated outlet box 15 when the unit 11 is installed therein in the conventional manner shown in FIG. 2. Thus, the receptacle 11 is provided with the conventional attaching lugs 21 at its opposite ends which are secured to subjacent lugs 22,22 of the outlet box 15 by fastening screws 23,23. When the receptacle 11 is installed in the box and secured thereto by the screws 23,23, the spring metal grounding clip 16, previously attached to the receptacle 11 by the terminal screw 14, as above described, engages the transverse wall 17 of the box at the contact loop 19 thereof and thus provides a ground connection for the receptacle 11.

It will be noted that the contact loop 19 includes a straight portion 24 adapted to engage the wall 17 with flat surface contact, being pressed thereagainst by the flexure of the offset portion 20 resulting from the securement of the receptacle 11 in the box 15, the offset portion 20 being of sufficient length to provide such spring tension. Thus, the spring tension holds the straight portion 24 against the inside surface of the transverse wall 17 and provides a firm and reliable ground connection at the region of contact of straight portion 24 with wall 17.

Referring now to FIGS. 4, 5 and 6, 30 designates a different type of spring metal grounding clip which may be employed, particularly where the receptacle or switch unit does not have a ground connection terminal 14. Thus, the unit, designated as 31 in FIGS. 4, 5 and 6, is provided with the supporting lugs 21,21 which form part of the metal frame structure of the unit 31 and which are employed in the same manner as previously described for securing the unit 31 to the anchor lugs 22,22 of an outlet box 15. The spring metal grounding clip 30 comprises a generally U-shaped main body of flat spring metal having the main-supporting portion 32 and the spring arm portion 33 integrally connected by the bight portion 34. The main supporting portion 32 is provided at its top end with a flange 35 which is generally T-shaped and provided with the opposing in-turned channel elements 36,36. As shown in FIG. 7, the flange 35 overlies the flexure arm 33. The channel elements 36,36 comprise bendable tabs which can be bent over the opposite side edges of a fastening lug 21 of the unit 31. Thus, in installing the grounding lug 30, the flange 35 is first placed beneath a lug 21 of the associated electrical unit 31 and the ends of the tabs are bent over the opposite edges of the lug 21 to define the channels 36,36, employing pliers or a similar tool to bend the tabs around the edges of said lug 21. This secures the flange 35 beneath the lug 21 with the portion 32 depending therefrom and with the spring arm 33 in a position to resiliently engage the transverse end wall 17 of the associated outlet box 15 when the electrical unit 31 is installed in the box. Thus, with the grounding clip 30 secured to the lug 21 as above described, the unit 31 is secured in the outlet box 15, employing the fastening screws 23,23 in the manner previously described. The arm 33 then engages the inside surface of the transverse wall 17 of the box with spring tension and provides a reliable grounding connection between the frame structure of the unit 31 and its associated outlet box 15.

It will be understood that the tabs, shown at 40,40 of the grounding clip 30 are normally flat but are bendable around the side edges of a lug 21 and can be clamped tightly to the lug 21 so as to substantially rigidly connect flange 35 to said lug 2. As previously mentioned, crimping action can be performed by any suitable tool, such as by a pair of pliers, or the like.

FIGS. 8, 9 and 10 illustrate another form of grounding clip, shown at 50, which may be employed to provide a ground connection between an outlet box 15 and an electrical unit 31 received therein. The clip 50 comprises a length of spring rod material, such as spring wire or the like, bent to form a downwardly facing generally U-shaped loop 51 adapted to engage over a longitudinal wall 52 of an outlet box 15 adjacent to a transverse end wall 17 thereof, and being adapted to clampingly engage the longitudinal wall 52. Thus, the loop 51 is made relatively narrow and of sufficient width to snugly receive the top marginal portion of the wall 52 with its bight portion 53 substantially in engagement with the top edge of wall 52. The leftward arm of the U-shaped element 51 is formed at its bottom end with a circular loop 54 adapted to engage the outside surface of wall 52 with flat surface contact, as is clearly shown on FIG. 9. The opposite arm of the U-shaped member 51 is reversely bent at 55 and formed at its top end portion with an upwardly and outwardly inclined spring arm portion 56 terminating in a circular end loop 57. Arm 56 normally projects upwardly and away from the inverted U-shaped portion 51 and is engageable beneath a lug 21 of the associated electrical unit 31 in the manner illustrated in FIGS. 8 and 9 when said electrical unit 31 is secured in the outlet box 15 by means of the fastening screws 23, as above described. Thus, arm 56 engages beneath a lug 21 and is held thereagainst by spring tension, thus providing the desired grounding connection between the lug 21 and the outlet box 15.

As previously mentioned, the inverted U-shaped member 51 engages over the wall 52 with firm frictional contact and is in effect clampingly secured to said wall. The clip 50 is thus held in a position wherein the spring arm 56 projects over the box 15 in a position to be engaged by one of the fastening lugs 21 of the associated electrical unit 31 when said electrical unit is secured in the box by means of its fastening screws 23. Therefore, when the electrical unit 31 is installed in its associated box 15, a grounding connection between the metal frame portion of the electrical unit 31 and the associated outlet box 15 is automatically provided.

In the preceding discussion, the apertured lugs 21,21 and, in the case shown in FIGS. 1 and 2, the terminal lug 13, are considered to be part of the supporting frame structure of the electrical unit 11, inasmuch as in many common designs of such electrical units the apertured lugs are extensions of the frame structure and the main body of the unit is molded or otherwise rigidly fastened to such frame structure with the lugs projecting at opposite ends of the electrical unit. The ground sockets contained in the recesses 12 are internally conductively connected to the frame structure. Thus, FIGS. 1 and 2 show one particular type of electrical unit in which the grounding lug 13 is actually an extension of the apertured supporting lug 21 and a fastening screw 14 is provided, whereby the embodiment of FIGS. 1 and 2, namely, the grounding device 16, is particularly appropriate for use. Other designs of electrical units, such as those shown in FIGS, 4, 5, 6 and 8, may not be provided with grounding lugs 13 and associated fastening screws 14, whereby it is more appropriate to employ grounding devices such as the device 30 or the device 50.

While certain specific embodiments of improved grounding devices for establishing a ground connection between an electrical unit, such as a receptacle, a switch, or the like, and a metal box member receiving such electrical unit have been disclosed in the foregoing description, it is understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitation be placed on the invention as defined by the scope of the dependent claims.

Claims

What is claimed is:

1. In combination with an electrical unit provided with a metal supporting frame member and a metal box member receiving said electrical unit, a grounding device comprising a metal body and a spring contact arm and means attaching said body to the metal supporting frame member in a position with said spring arm conductively engaging the metal box member, wherein said spring arm is integral with said metal body, wherein the electrical unit is of the type including apertured fastening lugs connected to said frame member and mounting screws extending through the apertures of the lugs securing the electrical unit to the metal box member, wherein said body is of flat spring metal stock, and wherein said body has a flange portion disposed beneath one of said fastening lugs and said attaching means comprises bendable tabs on opposite sides of said flange portion crimped around the side edges of said one of said fastening lugs.

2. The structural combination of claim 1, and wherein said flange portion overlies said spring arm.

3. The structural combination of claim 2, and wherein said body is generally U-shaped, with the flange portion at the top end of one side element of the body, said spring arm comprising the other side element of the body.